The present invention principally relates to theft prevention systems for trailers, particularly those used in a over-the-road tractor-trailer vehicle combination commonly referred to as an xe2x80x9c18-wheelerxe2x80x9d. These trailers are almost universally provided with pneumatic braking systems which include a parking/emergency brake with brake shoes or other braking elements urged to the braking position by spring means in the absence of pneumatic pressure supplied to the braking system.
In this common arrangement, a parked trailer being disconnected from the tractor vehicle with its source of air pressure will have its parking/emergency brakes (hereinafter simply xe2x80x9cparking brakesxe2x80x9d) urged to full braking position preventing the trailer from rolling or being moved. However, the commonly provided system can be moved by any standard tractor vehicle having the usual air hose and electrical connections for a trailer. Once the alien tractor is connected with its air hoses to the trailer and the trailer braking system is pressurized, the parking brakes air pressure causes the spring forces to be overcome so that the parking brakes are no longer applied.
Numerous expedients have been employed to prevent or deter theft of a parked trailer, including systems which require some action in addition to connecting air pressure to the pneumatic brake system to release the parking brakes. Some of the theft deterrent systems incorporate a solenoid valve in the appropriate air line between the tractor and the trailer rear wheels and have a key lock switch or other device required to energize the solenoid. The valve will open when the key switch is closed to allow air pressure from the tractor to release the brakes on the wheels of the trailer (as it would if the valve were not present). These prior systems typically drew current for the solenoid from the electrical cable providing power to the trailer lights, and thus some portion of the conductors of that cable needed to be connected and energized, but this in itself was not an anti-theft feature since this would occur in the course of normal procedure by the truck driver.
Systems as described above are shown, for example, in U.S. Pat. Nos. 4,793,661 and 4,712,422 to Douglas Munro. In these patents, the theft of the trailer is deterred by operation of a solenoid valve by a key operated switch on the trailer. Rather than being a key switch, the switch may take the form of a keyboard module switch operable only by a person in possession of the required key code. Note that the key-operated switch is on the trailer, and only standard equipment connections from a tractor are required so that an alien tractor can take the trailer if the operator is in possession of a key or a key code. U.S. Pat. No. 4,691,801 to Yale Mann and Pekka Sarssi describes a vehicle protection device which, in addition to a fuel valve block and other features, also has a parking brake lock for trailer brakes; all of these are operated by a portable infrared transmitter (rather than the key operated switch or keyboard module switch of the Munro patents). U.S. Pat. No. 5,378,929 to Yitzchak Mor and Daniel Yuranyi describes a somewhat more complicated system of valves and alarms than those discussed above whereby the system can be manually activated using a hand-held remote control transmitter and receiver (or a hard-wired switch) located somewhere in the trailer.
U.S. Pat. No. 4,621,874 to Jan Gustafsson is a vehicle theft preventing device for brakes operated with compressed air having a particular valve system and which requires the operation of a code lock on the trailer to release the brakes by pressing the correct code to adjust a valve to release the brakes. U.S. Pat. No. 3,735,834 to Daniel A. St. Onge describes a brake locking system with a key operated mechanism on the trailer required to close a normally open relay by use of a proper key; the valves of the system cannot be operated to admit air pressure to release spring force applying the brakes without such a proper key even though air pressure and EMF (through an electric cable) are connected to the vehicle. While it is known to transmit information between a truck tractor and trailer as disclosed in the U.S. Pat. No. 5,142,278 to Moallemi et al., such capability has not been used to set and/or release anti-theft devices in a trailer.
Other patents relevant to the background of the invention and to the state of the art are U.S. Pat. No. 4,519,653 to Paul B. Smith, U.S. Pat. No. 5,442,810 to Jenquin, and U.S. Pat. No. 4,881,388 to Ronald Pruim.
In addition to use of key-operated switches, numeric keypads for entry of key codes, or combination switches that may be used to generate a locking or unlocking signal in a vehicle security device, there are other security applications in which unauthorized operation is controlled by provision of a card reader which identifies an ID card of an operator seeking to operate the device. Such apparatus for management of the operation of a centrifuge is shown in U.S. Pat. No. 5,871,435 to Satoshi Numata, et al. Portions of such apparatus may be employed in an ID card reader version of Applicant""s invention. As evidencing the state of the art relevant to the enablement of Applicant""s disclosure, the Numata et al. patent, the Moalemi et al. patent and the other relevant patents above are to be considered incorporated by reference here.
The present invention is directed to a theft prevention system for tractor-trailer transport vehicles. In particular, such trailers usually employ an air brake system using two air lines where one parking air line controls the trailer""s parking/emergency brakes and another system air line controls the regular operating brakes. Air supplied by an air pressure supply means at the tractor controls both brake systems. In accordance with DOT specifications, the emergency brakes should set automatically when the trailer is parked and/or the air supply is disconnected. A major problem as mentioned above is that the thieves, if not otherwise deterred, can steal an entire parked trailer by coupling a tractor to the trailer, releasing the parking brakes in the customary manner, and driving away with the trailer in tow.
While previous anti-theft systems have provided locking means for parked trailers which prevented the release of parking brakes, the present invention has advantages and special features which primarily relate to a regimen of preventing alien tractors not belonging to a particular trucking company, and/or not connected by satellite in that company""s particular communication net, from releasing the parking brake in a trailer belonging to a trucking company equipped with the system of the present invention. The receiver and solenoid valve of the present invention are responsive only to a special transmitter installed in an authorized tractor. Thus, only authorized tractors with such special transmitter appropriately activated can couple to and successfully deactivate the parking brakes. Although a wireless transmitter in a tractor may be utilized to transmit the signal to release the parking brakes, it is preferred that a signal be transmitted over existing conductors in the electric cable connected to the trailer for controlling and powering the lighting of the trailer. Numerous types of tractor to trailer signaling, preferably digitally coded, may be employed including DC, AC, audio frequency and radio frequency transmission. The communication can accompany two-way communication of supervisory information other than anti-theft control (as in a system as shown in U.S. Pat. No. 5,142,278 or U.S. Pat. No. 5,442,810). The coding of the signal required by the receiver to actuate solenoid valves to control the emergency brakes can be as complex as desired to prevent would-be thieves from sending a false signal not originating from an authorized transmitter to release the trailer brakes. In a preferred embodiment, the electrical and pneumatic components of the system are configured so that continued receipt of the parking brake release signal is not required as long as air pressure to the trailer is maintained above a minimum value and the electrical power to the lighting system or theft prevention system are not interrupted.
A further feature of the system requires that the driver of the truck have a key, key code, key card or authorization communicated by satellite to activate the transmitter, rather than to simply flip a switch in the tractor cab. This gives additional security that upon gaining access to the tractor cab, one cannot release the tractor brakes without having necessary authorization.
In accordance with another optional feature of the system, the receiver and the decoder forming a part thereof may require that several or all of the trailer light circuits be energized to operate the solenoid brake release valve. Thus the driver could be required to test the lights before releasing the brakes. A more sophisticated version may require that trailer lighting circuits be energized in a particular sequence. In the latter case, this could operate as an additional xe2x80x9ccodexe2x80x9d making the theft of the trailer using an unauthorized tractor more difficult. The present theft prevention system has an advantage over previous systems in that it does not require removal, replacement or modification of the service trailer air brake system. It does not interact with the service line for the regular operating brakes at all and requires only the insertion of solenoid valves in the parking air supply lines which can be conveniently done near the point where such air lines enter the trailer. The theft prevention receiver unit of the present invention also requires a simple connection to two or more conductors of the standard electrical cable connected to the trailer to supply power to the various lighting circuits. The transmitter in the tractor cab only requires connection to the electrical system of the tractor, preferably being connected into a circuit or circuits for the trailer lights. The present invention provides a lock-open feature to allow normal parking brake operation without authorization signal from a tractor cab with an appropriate digital signal transmitter. This accomodates a need for a trailer with its load to be dropped off at a large warehouse or distribution center to later be moved from the drop yard to a loading dock or other unloading site by a warehouse tractor designated for moving and positioning trailers at the facility. In a preferred embodiment this drop yard feature is implemented by a locking element associated with a solenoid valve adapted to lock the valve in an open position or to unlock the valve in response to control signals from a receiver in the trailer. Also, the trailer solenoid may be provided with a bypass air line and a remotely operable control valve so that the theft prevention system can be effectively disabled if desired for the drop yard situation or other reasons without requiring the services of a technician. The bypass valve may include a manual valve preferably with a lock and/or within a locked cabinet. Preferably the trailer receiver and solenoid valve are positioned in a locked or secure cabinet to deter a thief from xe2x80x9chot-wiringxe2x80x9d or otherwise defeating the theft prevention system.
In addition to providing the features and advantages described above, it is an object of the present invention to provide a theft prevention system for tractor-trailer transport vehicles that is implemented with minimal modification of trucks or trailers by adding transmitters in the tractor cabs and receivers and solenoid valves in the trailers leaving the air line connections and electrical cable connections from tractor to trailer without modification and allowing a tractor to be coupled to a trailer in conventional fashion.
It is another object of the present invention to provide a theft prevention system in which an operator of an authorized tractor-trailer can connect a trailer to the tractor in customary fashion and, upon activation of a transmitter within the cab, proceed to release the parking brakes in the customary manner in a simple and expeditious manner.
It is yet another object of the present invention to provide a theft prevention system for trailers in which normally locked parking brakes in compliance with DOT specifications require for brake release that a signal be transmitted to a receiver in the trailer by activating a transmitter in the cab, and the action required by the driver to activate the transmitter is authorized by remotely transmitted data through a remote terminal in the cab.
It is a further object of the present invention to provide a theft prevention system for trailers having a solenoid valve in a trailer air line which must be open to release the trailer parking brakes wherein the solenoid valve has an integral pneumatic latch so that once opened by the solenoid, the valve is open as long as pressure is applied to the trailer parking brake air line.
It is a further object of the present invention to provide a remotely controlled element selectively to deactivate the anti-theft braking function for drop yard mobility or to activate it for over the road operation.
It is a still further object of the present invention to provide a theft prevention system for trailers having a solenoid valve controlling release of the parking brakes which is activated to release the brakes only upon energization of a plurality of the lighting circuits for the trailer.
Further objects and advantages of the present invention will be understood by those skilled in the art by reference to the following description and the appended drawings.